The present invention relates to a novel and improved chemical-amplification negative-working photoresist composition suitable for the formation of a photoresist layer on an undercoating of an organic anti-reflection film on the surface of a substrate to give a patterned resist layer of high pattern resolution and having an excellently orthogonal cross sectional profile.
Along with the trend in recent years toward higher and higher degree of integration in various semiconductor devices, the photolithographically patterned resist layer on a substrate surface is required to have a pattern resolution of as fine as 250 nm or, as a target in the coming generation, as fine as 200 nm. Needless to say, such an extremely fine pattern resolution of the patterned resist layer cannot be accomplished without an innovative improvement in the performance of the photoresist composition which may be a chemical-amplification negative-working photoresist composition.
The above mentioned chemical-amplification negative-working photoresist composition is typically formulated with an acid-curable alkali-soluble resin such as a phenolic resin, a radiation-sensitive acid-generating agent and a crosslinking agent for the resin such as an addition product of urea or melamine and formaldehyde. While it is essential for the formation of a latent image of the pattern that the pattern-wise exposure of the photoresist layer to actinic rays is followed by a post-exposure baking (PEB) treatment, it is known that the line width of the patterned resist layer is influenced by the temperature of the PEB treatment.
When the temperature of the PEB treatment deviates out of a certain range, an appropriate line width of the patterned resist layer as desired can no longer be accomplished and the troubles thereby are more serious as the fineness of patterning is increased. Accordingly, it is eagerly desired to develop a negative-working photoresist composition of which the patterning process can be performed with a greatly increased temperature latitude for the PEB treatment or, namely, the line width of the patterned resist layer is little affected by an increase or decrease of the PEB temperature.
On the other hand, it is usual that a photoresist layer of a chemical-amplification negative-working photoresist composition is formed not directly on the surface of a substrate but on an undercoating layer of an anti-reflection film of an organic anti-reflection compound formed on the substrate surface in view of the advantage relative to the pattern resolution which can be as fine as 200 nm or even finer.
It is sometimes the case, however, that, when a conventional chemical-amplification negative-working photoresist composition is used in combination with an organic anti-reflection coating compound in the form of a solution such as the most typical commercial products of the DUV Series products (each a product by Brewer Science Co.), an excellently orthogonal cross sectional profile of the patterned resist layer can hardly be obtained and the cross sectional profile is more or less trapezoidal or skirt trailing. Accordingly, it is one of the target problems in the development works for negative-working photoresist compositions to obtain a chemical-amplification negative-working photoresist composition capable of being used in combination with an organic anti-reflection coating compound without being influenced in the pattern resolution and cross sectional profile of the patterned resist layer.